Wood stain formulations are applied to exterior wood surfaces such as wood furniture or fixtures to extend the life of the wood surface, maintain the appearance of the surface, and/or to improve the performance or durability of the wood substrate. Exterior wood surfaces are exposed to extreme weather conditions such as snow, heat, sun, and rain, causing wood to be susceptible to mold, mildew, and damage from UV exposure. Wood stain formulations providing one or more functions such as stain resistance, mold and mildew resistance, antimicrobial properties, and pest resistance are used to extend the durability of the wood substrate.
Wood stain formulations may be oil based or solvent based systems. Oil based systems can require lengthy drying times. Non-aqueous solvent based systems may have shorter drying times, but are less ecologically friendly due to the use of solvent. In view of environmental legislation that has established limits on the amounts of volatile organic compounds (VOCs) which are allowed in different coating systems, there has been a shift away from solvent borne coatings to water borne systems.
Water based coatings are more ecologically friendly. However, one disadvantage of waterborne coatings is that such coating compositions dry at a rate which depends on the temperature and humidity of the coating environment. Under low humidity conditions, waterborne coatings may dry rapidly. However, at higher atmospheric humidity, drying times are longer due to the slower evaporation of water from the coating composition. As such, certain water based coatings become water resistant only after extended drying times.
Wood stain formulations typically require the substrate to be dry before coating, which often means that the user must wait one to two days for the substrate to dry before applying the coating. Some wood stain formulations also prescribe that coatings may be applied only within certain temperature ranges, and only if rain is not expected for the next 24 hours or more.
Current aqueous coating compositions are disadvantageous because they require a sufficiently dry substrate, and/or rain free weather conditions post application, as well as drying times that are dependent on temperature and humidity conditions.
Accelerated drying of waterborne coating compositions which do not require the substrate to be dry prior to application, and can dry rapidly even under high atmospheric humidity is desirable.
Attempts have been made to improve drying times of aqueous coatings by incorporating a quaternary poly(allylamine) into the coating compositions as a drying accelerator. U.S. Pat. No. 7,071,260 relates to rapid-curing aqueous coating agents containing at least one binding agent and at least one water-soluble, quaternary poly(allylamine). However, such coating compositions are not suitable for weatherproof type of application and requires additional emulsifier to incorporate the quaternary poly(allylamine).
Other approaches to improving air drying times include the use of an air drying agent by reaction of epoxy containing polyacrylates, fatty acid, and monoamine ammonium salts. U.S. Pat. No. 5,089,342 relates to an aqueous coating agent for providing a decorative and protective coating for wood or wood products which contains as a binder, polyacrylate resins having chemically incorporated therein air-drying, unsaturated fatty acid moieties and quaternary ammonium moieties.
U.S. Pat. No. 5,284,690 describes an article comprising an aqueous release coating which includes a polymer and an aqueous solution or dispersion of an organic compound having at least one fatty acid ester and at least one quaternary amine.
BE1014749 relates to an additive for coating compositions comprising nonionic and/or cationic surfactant, alkali metal metasilicate, alkali metal gluconate, glycol, and water.
U.S. Pat. No. 6,077,888 relates to bituminous emulsions which can be used to produce bituminous emulsions exhibiting high viscosity and low asphalt residues. The emulsifying compositions are combinations of fatty amine and/or polyamine, lignin, and non-ionic surfactant.
Accordingly, there is a need for weatherproof coating systems which allow the user more flexibility in coating exterior substrates, such as by providing faster drying times without requiring the substrate to be dry prior to application, and without requiring the coated substrate to remain dry post application.